Arrhythmias Flashcards
State the tachyarrhythmias you need to know
Supraventricular tachycardias
- Sinus node
- Sinus tachycardia
- Atria
- Atrial fibrillation
- Atrial flutter
- Atrial tachycardia
- AV node
- AV nodal re-entrant tachycardia
- Atrio-ventricular re-entrant tachycardia
Ventricular Tachycardias
- Ventricular tachycardia (monomorphic)
- Torades de pointes (polymorphic VT)
- Ventricular fibrillation
What is the commonest cardiac arrhythmia encountered in clinical practise?
Atrial fibrillation
Does prevalence of AF increase with age?
Prevelance of AF increases with ageadn the incidence of AF is suspected to increase steadily
AF can be described as paroxysmal, persistent or permanent- describe each
- Paroxysmal: intermittent episodes which self-terminate in 7 days (typically self terminate in <24hrs)
- Persistent: prolonged episodes that can be terminated by electrical or cardioversion (last >7 days)
- Permanent: cannot be cardioverted or if attempts to do so are deemed inappropriate
Describe the pathophysiology of AF
- Complex arrhythmia characterised by both abnormal automatic firing and presence of multiple interacting re-entry circuits around atria
- The disorganised electrical activity overrides normal organised activity from SA node
- This is leads to uncoordinated, rapid and irregular contraction of atria
- The AV node responds/conducts impulses intermittently leading to irregular contraction of ventricles
State some risk factors/causes of AF
*HINT: the atrial fibs
- Thyrotoxicosis
- Hypothermia, hypertension, heart failure
- Embolism (PE)
- Alcohol
- Trauma (cardiac)
- Recent surgery (cardiac)
- Ischaemia or infarct
- Atrial enlargement
- Lone or idiopathic
- Fever, anaemia, high output
- Infection (e.g. sepsis)
- Bad valves (e.g. mitral stenosis)
- Stimulants (e.g. cocaine, amphetamine, caffeine)
- ****NOTE: there are lots of causes for AF. Can use mneumonic but also useful to structure via systems as in the image below.*
- ***Can also use Mrs SMITH from ZtoF: sepsis, mitral valve pathology, ischaemic heart disease, thyrotoxicosis, hypertension*
Describe the typical presentation of AF
Pts often asymptomatic and AF picked up incidentally; however, pts may experience:
- Palpitations
- Dyspnoea
- Syncope (dizziness or fainting)
- Chest pain
- Symptoms of associated conditions (e.g. sepsis, stroke, heart failure, thyrotoxicosis etc..)
What might you find on clinical examination of someone with AF?
- Irregularly irregular pulse
- Tachycardic
- 1st heart sound of variable intensity
- Signs of underlying cause (e.g. heart failure, thyrotoxicosis, PE, mitral valve disease)
What other arrhythmia could an irregularly irregular pulse be (aside from AF)?
Ventricular ectopic beats
What investigations would you do for suspected AF, include:
- Bedside
- Bloods
- Imaging
*Justify each where appropriate
Bedside
- ECG: show AF
Bloods
- FBC: raised WCC in infection
- U&Es: assess electrolytes & can be helpful for choosing anti-arrhythmic
- TFTs: thyrotoxicosis may present as AF
- Cardiac enzymes: myocardial ischaemia may be caue of AF
- NT-pro BNP: suspect heart failure as cause
Imaging
- CXR: may show precipitating factor such as pneumonia, heart failure
- ECHO: help identify cause e.g. mitral valve pathology, heart failure
Describe what you would see on the ECG of AF
- Rate: tachycardia
- Rhythm: irregularly irregular
- P waves: absent
- QRS: <120ms
If paroxysmal AF is considered, what further investigations would you want?
- Short term cardiac monitoring with 24hr cardiac monitor (symptoms would have to be very freuqent for you to catch the arrhythmia)
- AliveCor app/cardiac monitor (often used in primary care)
- Prolonged cardiac monitoring such as Holter monitor or implantable loop recoder
State the two main principles in the treatment of AF
- Rate or rhythm control
- Rhythm control means putting back in sinus rhythm. This could be through a single cardioversion event (which can be electrical or pharmacological) or long term medical rhythm control using medications
- Anticoagulation to prevent stroke
Explain why we want to control the rate in AF
- In AF, atria ‘quiver’ this means ventricles don’t fill with blood as efficiently
- Furthermore, since heart rate is higher in AF ventricles have less time to fill- further decreasing the effectiveness of ventricular filling in AF
- Since ventricular filling isn’t as efficient, pre-load decreases resulting in decreased SV and cardiac output
- Decreased CO can lead to myocardial ischaemia and potentially infarct
- Aim of rate control is to get HR <100bpm to increase time for ventricular filling
What are the two main options for rhythm control in AF?
- Cardioversion (electrical or pharmacological)
- Long term medical rhythm control
NICE (2014 guidelines) recommends all pts with AF should have rate control as first line unless what? (4)
- There is a reversible cause for their AF (reverse cause and see if AF resolves)
- The AF is of new onset (within last 48hrs. Can be heparinised and cardioverted using electrical or pharmacological cardioversion. Could be rate controlled instead though)
- Heart failure thought to be primarily caused by AF/coexistent heart failure
- They remain symptomatic despite being effectively rate controlled
- Unstable/adverse features (as per ALS guidelines):
- Shock
- Syncope
- Heart failure
- Myocardial ischaemia
If a pt with atrial fibrillation has unstable/adverse features (shock, syncope, myocardial ischaemia or heart failure) what should you do?
Pt should be electrically cardioverted (as per the peri-arrest tachycardia guidelines)
State what drugs we can give to pts with AF for rate control
- First line= beta blocker (e.g. atenolol 50-100mg once daily) or non-dihydropyridine CCB (e.g. diltiazem)
- Digoxin (only in sedentary people/people who do little to no exercise- needs monitoring as risk of toxicity. May be beneficial if co-existent heart failure)
NICE state that if one drug doesn’t adequately control the rate than can use combination of 2 of the above.
Discuss the difference between immediate and delayed cardioversion including:
- Who offered to
- Any treatment required in mean time
Immediate Cardioversion
- AF present for <48hr or pt severely haemodynamically unstable
- Unlikley they have developed a blood clot in 48hr hence don’t need antiocoagulant prior to cardioversion
Delayed Cardioversion
- AF present for >48hr and pt is stable
- Pt needs to be anticoagulated for at least 3 weeks prior to cardioversion as they may have developed a clot in atria and reverting them back to sinus rhythm carries high risk of mobilising the clot causing a stroke. Pts should have rate control whilst waiting for cardioversion
What is an alternative strategy to anticoagulating patients with AF for >48hrs for 3 weeks prior to cardioversion?
Transoesophageal echo to exclude left atrial appendage
If there is a high risk of cardioversion failure, what is recommended?
Amiodarone or sotalol for at least 4 weeks prior to electrical cardioversion
State what two drugs can be used for pharmacological cardioversion
Describe what is involved in electrical cardioversion
Pharmacological Cardioversion
Agents with proven efficacy:
- Flecainide (if no structural heart disease)
- Amiodarone (drug of choice in pts with structural heart disease or co-existing heart failure)
Agents deemed less effective:
- Beta blockers
- CCBs
- Digoxin
- Procainamide
Electrical Cardioversion
- Rapidly shock heart back into sinus rhythm (synchronised to R wave)
- Give pt sedation or general anaesthetic and use cardiac defibrillator to deliver controlled shocks in attempt to restore sinus rhythm
Discuss whether anticoagulation is needed after electrical cardioversion of AF
- If AF <48hrs and electrical cardioversion performed, anticoagulation is unnecessary
- If AF >48hrs, anticoagulation for at least 4 weeks then reassess
*NOTE: NICE recommend electrical cardioversion if AF >48hrs
What drugs can be used for long term medical rhythm control if cardioversion is not an option
- First line= beta blockers
- Second line in patients following cardioversion= dronedarone
- If pt have HF or LVD= amiodarone
What do NICE recommend considering if AF has not responded to or wish to avoid antiarrhythmic medications?
- Percutaneous catheter ablation (can use radiofrequency or cryotherapy)
- Anticoagulate for 4 weeks prior to procedure then after procedure for at least 2 months (duration depends on CHA2DVASC)
Discuss what treatment we can offer to pts with paroxysmal AF
- Paroxysmal AF (arrhythmia self terminates within 7 days- but usually within 48hrs).
- Offer pt “pill in pocket” approach; pt takes a pill to terminate AF when they feel the symptoms of AF starting
- Flecanide is drug of choice
- In order to be suited for pill in pocket approach pt needs to have:
- Infrequent episodes
- No underlying structural heart disease
- Need to be able to identify when in AF
What score calculates stroke risk in patients with atrial fibrillation?
What do the following CHA2DVASC scores suggest regarding anticoagulation:
- 0
- 1
- ≥ 2
- 0 = no treatment
- 1 = in MALES consider anticoagulation, in FEMALES no treatment
- ≥2 = offer anticoagulation
**REMEMBER: if CHA2DVASC score suggests no need for anticoagulation must ensure transthoracic echo done to exclude valvular heart disease which in combination with AF is absolute indication for anticoagulation